1. Field of the Invention
The present invention relates generally to devices and methods for selecting an intraocular lens and more specifically to devices and methods of finding suitable powers and/or locations of intraocular lenses to be implanted into an eye in order to obtain a predetermined refractive outcome, taking into account such parameters as the asphericity of the cornea and/or the intraocular lens.
2. Description of the Related Art
U.S. Pat. No. 5,968,095, herein incorporated by reference, refers to a method of preoperatively selecting the power of an intraocular lens (IOL) to be implanted into an eye having a lens haptic plane. The method involves selecting eye parameters to construct an eye model for finding a correct representation of the intraocular lens as axially positioned in the eye following surgical implantation. However, this method is not designed to be applicable when any of the optical surfaces is aspheric. In particular this method is not applicable when using aspheric lenses designed to reduce or eliminate the spherical aberration of the cornea. Other commonly applied methods to determine IOL power, such as the widely used SRK/T formula, and other widely applied methods such as the Hoffer Q and Holladay 1 and Holladay 2 formulas, suffer the same shortcoming in being based on thin lens vergence calculations and/or spherical lens surfaces. Paul-Rolf Preussner et al. disclose an alternative method of predicting outcome of choice of IOL model and power in J Cataract Refract Surg, 2004, Vol. 30, pp. 2077-2083, which is herein incorporated by reference.
As aspheric IOLs capable of correcting spherical aberrations now are becoming available on the market (e.g., Tecnis® brand of IOL, available from AMO Inc., Santa Ana, Calif.), there is a demand to obtain reliable methods to select aspheric IOL powers in order to achieve the desired patient outcome in terms of spectacle correction and/or image quality.